In the dental field it is now well recognized that the alloy to which low-fusing porcelain can be successfully applied so as to have complete adhesion must be compatible from the standpoint of coefficient of linear expansion and contraction at the fusing temperature of the porcelain; and that such alloy must provide on its surface oxides which facilitate the adhesion of the porcelain.
It is also well understood that after application of the porcelain to the alloy, the porcelain surface should not check, crack or separate from the base alloy.
There are on the market today various opaque porcelains which are especially prepared and sold for application to dental alloys. The opaqueing materials of such opaque porcelains vary from one to the other and the basic ingredients of such opaque porcelains are not fully disclosed in any literature with which I am familiar. Essentially all opaque porcelains for dental application are said to be low-fusing in that they will fuse at a temperature of about 1800.degree. F. to dental alloys and will adhere to the same provided all other conditions are met for fusing such porcelains to the metal alloy.